I decided to defrag my HD...for the first time since 3 years (I know I know)! :-[
Its been runnning since 27 hours now and only 45% are completed...is that normal?
I would say no, that's not normal for your HDD size and CPU speed. However, I've never defragged one after 3! years. Depending on how much of that 120GB is full, I would expect several hours minimum, one day max, and that's generous.
Nothing to worry about, as long as the defrag isn't hung up and stopped working you're in good shape. Next time you do it (next week or month!!), it shouldn't take more than an hour or two, if that.